Problem: $\dfrac{2}{10} + \dfrac{1}{5} = {?}$
Solution: ${\dfrac{2}{10}}$ ${\dfrac{1}{5}}$ $+$ ${\dfrac{2 \times 1}{10 \times 1}}$ ${\dfrac{1 \times 2}{5 \times 2}}$ $+$ ${\dfrac{2}{10}}$ ${\dfrac{2}{10}}$ $+$ $ = \dfrac{{2} + {2}}{10} $ $ = \dfrac{4}{10}$